The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A hybrid electric vehicle (HEV) may include a powertrain system with multiple electric motor and/or generator units (MGUs) and an internal combustion engine (ICE). The MGUs and the ICE are used to provide torque to an electrically continuous variable transmission (EVT). The HEV may operate in an electric vehicle (EV) mode or in a hybrid mode.
The EV mode is used to conserve fuel. The engine is stopped (e.g., crankshaft of ICE stopped or rotating at approximately 0 revolutions-per-minute (rpm) and ignition disabled) when in the EV mode. Vehicle propulsion torque is provided by one or more of the MGUs when in the EV mode. A control module may switch from the EV mode to the hybrid mode when an increased torque output request (e.g., vehicle operator “tip-in” on an accelerator pedal) is received and/or due to a depleted state of charge (SOC) of an energy storage system. A “tip-in” event may refer to when an accelerator pedal is actuated by a vehicle operator and/or when the accelerator pedal is actuated past a predetermined pedal position. The control system may switch to the hybrid mode, for example, when battery SOC level is less than a predetermined threshold.
The hybrid mode is used, for example, when power storage levels of a battery pack are less than a predetermined threshold. The engine is running (e.g., operating at a speed greater than 0 rpm and ignition is enabled) and vehicle propulsion torque is provided by a combination of torque from the engine and one or more of the MGUs when in the hybrid mode.
Incorporation of multiple MGUs and an EVT allows for variable adjustment in engine speed. This provides engine speed adjustment at a certain vehicle speed for improved fuel economy. A HEV can experience large levels of changes in vehicle acceleration (“vehicle jerks”) when switching operating modes from, for example, the EV mode to the hybrid mode. The vehicle jerks due to the engine start may have an oscillatory signal profile due to pumping forces including compression forces within the ICE.